1. Field of the Invention
The present invention relates to a curable composition and method for producing a soft, yet solid elastomer in-the-ear product yielding the user greater comfort and durability. Additionally, the nature of the inventive soft body design provides better acoustic performance for a variety of ear canal shapes and various motion affecting the ear canal, such as head and jaw movements.
The present invention also provides for ear-worn configurations of subminiature electronic devices requiring discrete coupling to the ear. These devices include digital cellular telephone ear connections, ear plugs, headsets and ear phones for telecommunications, radio, television or computers.
2. Brief Description of Related Technology
Hearing aids need to be durable, comfortable and reliable. Durability focuses on the integrity of the material, long lasting, and integrity of the bonding of the components. Comfortability implies that the device is soft when placed in the ear canal. Reliability implies superior acoustic quality throughout the life of the device, which requires adequate sealing within the ear canal. The challenges to satisfy the comfort and reliability objectives are due to the dynamic nature of the ear canal, and the geometric alterations of the ear canal due to natural anatomical movement. The dynamic nature of the ear canal varies from person to person, and even the anatomical shape varies from ear to ear of the same person. The canal shape is geometrically altered by motion from the head and the mandible, usually causing elliptical elongation. These differences in canal shape and changes due to body movement make it difficult to achieve a comfortable and true acoustic seal.
Challenges in meeting comfort as well as durability are due to the nature of the ear canal and materials able to use. In the past, hearing aids were made from hard acrylic materials which have proven to be durable but uncomfortable. And when the device was displaced by motion, a leakage of sound pressure occurred. Attempts were made to use rubber instead of the hard acrylic materials, such as in U.S. Pat. No. 3,527,901 to Geib. Rubber is softer and more resilient than hard acrylic but it is not very comfortable and still lacks a true acoustic seal upon motion.
Attempt to use soft vinyl materials have also not been entirely successful in meeting the aforementioned characteristics. Although vinyl may be softer than rubber and offers a better acoustic seal, soft vinyl lacks durability, and in fact, after a relatively short period of time it shrinks, turns yellow and becomes hard or brittle. It is recommended in the hearing aid industry to replace vinyl components for behind-the-ear ear molds at least annually.
Silicone materials have also been used as the housing material, such as disclosed in U.S. Pat. No. 6,022,311 to Juneau, et al. The ""311 patent discloses a two layer silicone housing bonded with an adhesive to the plastic faceplate of the device. Although silicone has a longer wear life than vinyl materials, it lacks strong bonding properties to the plastics commonly used in hearing aid instrumentality.
Polyurethanes have in the past been used for hearing aid components. For example, U.S. Pat. No. 5,763,503 to Cowperthwaite, et al. discloses a housing for an in-the-ear hearing aid made from a solid and stiff polyurethane, polyesters or polyether to support the instrumentality. The Shore D hardness is from 50 to 90. Polyurethane has been proven to provide a better acoustic seal than polyvinyl. The properties needed for the housing require a stiff, firm, harder material to support the instrumentality which conflict with the objective for softer, comfortable fit within the ear canal.
Thus, instead of focusing on the housing material attempts have been made to supply an attachment to the housing such as a covering or sleeve. This preserves the durability of the original housing material, while adding a comfort factor. For instance, U.S. Pat. No. 4,870,688 to Voroba, et al. discloses a soft, resilient covering which is affixed to the rigid bonding of the ear shell. No covering material or details on affixing the covering to the ear shell were disclosed. Another example, U.S. Pat. No. 5,002,151 to Oliveira, et al., discloses a disposable sleeve made of a soft polyurethane retarded recovery foam attached to the ear piece by mating of screw threads on the sleeve and the ear piece. Unfortunately, a sleeve concept would lack durability and require continual replacement. The sleeve creates a safety concern due to the possibility of this attachment to slip off from motion in the ear canal and possibly lodging in the ear canal. The inadequacy and quality of the disposable sleeves bond to the housing is a major concern.
Softer materials than the housing have been used to create a tip portion. The tip portion is a hollow body which extends into the canal for the acoustic signal to pass through. Some known examples follow.
U.S. Pat. No. 6,205,227 to Mahoney discloses a relatively flexible tip which is rigid enough to prevent collapse of the passageway for acoustic signals. The tip disclosed has protruding fins for a better fit and is attached to the housing by a snap or a screw for easy removal and replacement. No material for the tip was disclosed.
U.S. Pat. No. 5,201,007 to Ward et al. discloses an ear mold with an acoustic conduction tube inside and a flexible flanged tip. The flange is used to hold the tip in place within the canal. The ear mold is constructed of silicone, polyvinyl or soft acrylic. The tip is connected to the tube by adhesive or heating.
U.S. Pat. No. 4,375,016 to Harada discloses an ear tip having a bulbous tip portion with a sound delivery aperture and vents for apertures. The ear tip is constructed of vinyl, silicone, plastic or foam. No means of connecting the tip to the housing is disclosed.
The same inadequacies found in the attempts to make a soft sleeve are found in the attempts to make soft tips. The current material of construction for a soft tip offers more comfort and better acoustic delivery than the hard acrylic shell. Unfortunately, the tip is less durable due to the inadequate bonding properties of the tip material to the housing material. There exists a potential for the tip to become dislodged within the ear canal from the constant motion in the ear canal and strain on the adhesive bond or mechanical bond.
There is a need for a soft tip on a sufficiently rigid housing which is durable, long-lasting material and strong bonding properties; comfortable, soft enough; and reliable, superior acoustics. The prior attempts noted above at satisfying these properties were seemingly unsuccessful. The present invention meets these and other needs.
In one aspect of the invention, there is provided a curable composition which includes a urethane acrylate oligomer, a reactive plasticizer or reactive diluent and a cure system. The function of the reactive plasticizers or diluent is to lower the hardness of the curable composition to provide a softer composition having a Shore A hardness of about 55 or less once cured. Softness, as defined by the present invention, is represented by the Shore A durometer scale. Specifically, in the present invention softness is defined as having a Shore A of about 55 or less.
In another aspect of the invention, there is provided a curable composition of Shore A hardness of about 55 or less which includes di-functional urethane acrylate oligomer present in amounts of about 35% to about 43% by weight; mono-functional urethane acrylate present in amounts of about 15% by weight; a reactive plasticizer or diluent is present in amounts of about 35% to about 43% by weight; and a photoinitiator is present in amounts of about 5% by weight.
In another aspect of the invention, there is provided a composition which includes a reaction product of a urethane acrylate oligomer and a reactive plasticizer or diluent wherein the reaction product exhibits a Shore A hardness of about 55 or less.
In yet another aspect of the invention, there is provided a method of making a soft tip hearing aid component which includes the steps of: combining a curable composition, which includes urethane acrylate oligomer, a reactive plasticizer or diluent, and a cure system component; pouring the curable composition into a mold; and exposing the curable composition to photo-radiation for a time and intensity sufficient to cure the composition to a Shore A hardness of about 55 or less.
In still another aspect of the invention, there is provided a hearing aid component which includes a urethane acrylate oligomer, and a reactive plasticizer or diluent to lower the hardness, soften the cured composition to a Shore A hardness of about 55 or less.
In a final aspect of the invention, there is provided a hearing aid assembly which includes an amplifier means for receiving and amplifying unamplified sound; a tube adapted to conveying amplified sound from the amplifier means to a first end of the tube inside the ear canal; a soft tip enclosing the tube wherein the tip""s composition includes a urethane acrylate oligomer, a reactive plasticizer or reactive diluent to decrease the hardness or soften the composition of the tip to a Shore A hardness of about 55 or less upon cure; and a housing comprising a cured monomeric material enclosing the amplifier means and the mating to the soft tip.